On any given, relatively warm winter day, the melodies of song sparrows and chickadees float down from the trees.

Hearing birdsong in early winter is both a natural and unnatural phenomenon, according to ornithologists. As days get longer and warmer, the birds’ internal clocks urge them to sing.

That’s why you may hear birds that live here year-round, like the chickadee, or that winter here but breed father north, like the American robin, sing during nice weather, according to Salve Regina University professor Jameson Chase. “So, not unusual and certainly not on warm days.”

But with spring-like weather coming earlier and earlier due to climate change, some of the songs of the season may be coming a little earlier, too.

“They are probably singing earlier,” Katie Schroeder, a graduate student at the University of Massachusetts Amherst who has studied song sparrows, told ecoRI News. Birds start to sing as soon as they get to their breeding grounds, and some birds are arriving earlier to these areas.

“We’ve got a warm winter, so there are things singing all the time,” said Pam Hunt, a conservation biologist at New Hampshire Audubon. “There are species that maybe started moving north a month early” to breed.

“It’s a lot of stuff kinda getting their little hormonal cycles jump-started,” she added.

On top of warm temperatures, artificial light can cause songbirds to start singing during off-times during the year, said Paul Miller, a board member of the Ocean State Bird Club.

(Artificial lights have also been known to disorient migratory birds and cause collisions.)

Sometimes though, the birds singing now might just be practicing, Miller said. They have to keep their vocal cords in good working order for breeding season, or they can atrophy.

Miller likes to compare some songs to the way humans get excited over a warm February afternoon; the birds start chirping to say, “Yeah, it’s a nice day!”